1. Field of the Invention
The present invention relates to a conductive polyurethane foam and its manufacture, and particularly to a conductive continuous foaming type polyurethane foam in which the surfaces of cells are covered with a pyrrole compound polymer and its manufacture, and further, to a method of continuously manufacturing a long-sized conductive continuous foaming type polyurethane foam sheet.
The present invention is applicable for antistatic fillers in the electronic and electric fields, antistatic cushioning materials for transport packages, sponge rolls for removing electrostatic charge, pressure sensors, pressure switches and the like.
2. Description of the Related Art
In recent years, conductive polymers such as polyacetylene have been synthesized. First of all, polymers of complex five-membered ring compounds such as pyrrole compounds have been focused in terms of electric conductivity and stability. The polymerizing method for the above-described polymers includes chemical solution polymerization, electrolytic chemical polymerization and interfacial polymerization. However, the conductive polymer is generally infusible and insoluble, and has a problem in workability. Further, the finished configuration of the polymer is limited to a film or powder state and the mechanical strength thereof is not strong so much. Consequently, the conductive polymer has been used as a complex material with a polymer base material excellent in workability and mechanical strength.
As techniques of manufacturing a conductive polyurethane foam complex, there have been known (1) an impregnation method (chemical solution polymerization) (Japanese Laid-open Nos. HEI 4-1241 and SHO 63-128034); and (2) a combination of the impregnation method and an electrolytic chemical polymerization method (Japanese Laid-open No. SHO 61-218643).
Further, there has been known a vapor phase method of forming a conductive polymer layer on a porous base material other than a polyurethane foam by vapor phase polymerization (Japanese Laid-open Nos. SHO 62-84115 and HEI 1-134805).
In the conventional impregnation method, since a base material is first impregnated in an oxidizer solution and subsequently dipped in a pyrrole solution, part of an oxidizer is added into the pyrrole solution so that pyrrole is naturally polymerized, to reduce the utilization factor of the pyrrole. Pyrrole generally contains an anti-oxidation agent, and thereby it must be refined before being used. The pyrrole thus refined is limited in its preservation period. Further, the interior of each cell of a polyurethane foam is almost filled with the pyrrole solution, and polypyrrole tends to grow in a massive state irrespective of the adhesion with the cell skeleton in the cell, which permits the polypyrrole from being easily fallen from the cell, thus exerting adverse effect as conductive impurities and dusts.
The above-described electrolytic chemical polymerization method is not suitable for the mass-production because the magnitude of a compound material is dependent on the electrode used. Further, the above-described vapor-phase polymerization method does not exemplify any polyurethane foam as the base material, and does not intend to obtain the sufficient solvent recovery.